The present invention relates to a heat exchanger and, more particularly, to a solderless heat exchanger which is assembled with mechanical measure such as tube expansion or the like, without using any soldering, suitable for use as radiator of automobile engine, warm-water circulation type heat radiator of air conditioner or the like purpose.
FIGS. 1 and 2 show the connection between a header plate 5 and a tube 1 in a conventional heat exchanger. In this connecting construction, an elastic sealing member 6 is interposed between the collar portion 5a' of the header plate 5 and the end portion 1a of the tube. This arrangement provides a sufficiently large buffering effect against external force but the number of parts is impractically increased to incur a rise of the production cost, as well as an increase of the weight. Further, the elastic sealing member 6 which is usually made of high molecule compound of rubber group does not have sufficient durability under a high temperature and chemical environment.
FIG. 2a shows another known heat exchanger disclosed in the specification of U.S. Pat. No. 4,159,741. In this known heat exchanger, it is extremely difficult to obtain a dynamical balance of the force caused by the permanent deformation of the tube end when the tube is expanded, within the region of elastic deformation of the header plate collar 5a', so that an extremely high precision of work is required in the fabrication of the heat exchanger. This not only makes the fabrication difficult but also poses a problem that the sealing effect is deteriorated due to an insufficient surface pressure (See FIG. 2b) when the above-mentioned dynamical balance is lost.
Furthermore, since the surface pressure of the joint surface A is drastically changed at an intermediate point as shown in FIG. 2b, the header plate 5 suffers a fatigue to reduce its durability, particularly when the heat exchanger is used under such a condition as involving continuous vibration and torsion as in the case of the radiator of automobile engine.